1. Field of the Invention
The present invention relates to an entirely novel type of skin-whitening agent which suppresses melanin polymer formation through trapping of melanin monomers, in particular, to a skin-whitening agent characterized in that it comprises as its effective ingredient a group of substances which bear the property of forming chemical complexes with melanin monomers.
2. Description of Prior Art
Various researches have been carried out for skin-whitening agents which may eliminate pigmented spots on human skin such as melasma and freckles, as well as enhancing throughout the whole skin the ability of retaining both beauty and whiteness. It is said that several factors such as melanin, carotene, blood stream level, skin thickness and skin transparency are involved in the color tone of healthy human skin. Among these factors, the level of eumelanin and pheomelanin are also known to be a major cause of pigmentation. Researches for skin-whitening cosmetics have also long been carried out: Such cosmetics are directed at suppressing the formation of melanin, a cause of melasma and freckles, as well as to enhance throughout the whole skin the ability of retaining both beauty and whiteness.
Recently, as to the process of forming melanin polymer in animal and human, in addition to the conventionally known pathway wherein tyrosinase participates, the presence and role of further critical pathways after DOPAchrome and their regulating enzymes are currently being clarified: Such pathways are those which proceed via two distinct types of melanin monomers, i.e. DHICA (5,6-dihydroxyindole-2-carboxylic acid) and DHI (dihydroxy-indole), while these two melanin monomers regulating enzymes are those including DOPAchrome tautomerase and DHICA-oxidase.
Various tyrosinase inhibitory compounds including kojic acid have been used as a means of suppressing the formation of melanin: Such compounds however have the disadvantage of being unsatisfactory in efficacy or lacking rapid effectiveness. Thus, there have been great expectations for the development of skin-whitening agents which are capable of achieving consistently high efficacy through any novel action mechanisms.